In the short, 0 48 hour lead time range forecasts over
the Pacific coastal area are adversely affected by the
sparsity of in situ observations over the upstream northeast
Pacific basin. The relative disadvantage of the west
coast areas arising from their geographical location
can be ameliorated by enhancements in the observational
network over the northeast Pacific. Since additions
to the permanent observing network would be prohibitively
expensive, research have focused on the use of adaptive
observing techniques where data are collected only prior
to threatening weather events, and only in areas critical
to the development of those events. EMC scientists,
in collaboration with university researchers, developed
adaptive observational techniques for this purpose.
The techniques have been tested in the course of other
field programs using NOAA aircraft.

Based
on the positive results from the field programs, in
1999 the National Weather Service established the Winter
Storm Reconnaissance (WSR) program. This is an annual
wintertime program where the NOAA G lV and USAF Reserve
C 130 planes collect dropsonde observations for the
purpose of improving winter storm forecasts. After streamlining
its procedures, the WSR program became operational in
2001. The G-IV operated from Honoulu, HI and Anchorage,
AK in January-March, 2002 conducting a total of 155
hours. In the operational WSR program, threatening winter
weather events are identified by NWS WFOs, and NCEP
Service Centers (primarily HPC). The Senior Duty Meteorologist
(SDM) of NCEP collects the requests for extra observations,
and through the use of special, ensemble forecast based
software, determines the optimal location of the adaptive
observations. The request for extra observations are
then relayed, through CARCAH, to the NOAA and USAF flight
facilities in terms of one or two of the 50 or so predesigned
northeast Pacific flight tracks.

The results from seven research and operational field
programs indicate that in 70 90% of the cases adaptive
observations improve the forecasts for the targeted
weather events. On average, a 10 20% error reduction
is observed in the targeted forecasts. As a result,
numerical forecast guidance issued 48 hours prior to
the events become as accurate as 36 hour lead time forecasts
without the use of adaptive observations.

Currently,
the WSR program runs for a 60 day period each winter,
and covers the 24 60 hour forecast lead time range over
the Pacific coast. Plans are being developed for the
expansion of the program to cover a 120 day period.
Also, research planning is underway to explore the expansion
of the program to the shorter, 12 24 hour lead time,
and smaller spatial scales. With these additions, the
WSR program would fulfill, at least during wintertime,
the NWS Strategic Goal of "Improved Numerical Weather
Prediction (NWP) over the Pacific/West Coast areas".